Cathode-ray tube having antenna getter with bimetallic insertion device

ABSTRACT

In cathode-ray tubes provided with an antenna getter on an electron-gun structure, a cathode-ray tube having antenna getter structures so improved in construction that, when the electrongun structure is advanced for insertion into said cathode-ray tube, there will be eliminated contact between the getter structures and a conductive coating on the inner surface of the tube wall, thereby to protect the conductive coating from coming off or being damaged, whereby deterioration in the innerelectrode insulation due to release of fine particle of the coating into the tube and the consequent in-tube discharge phenomenon may be prevented.

United States Patent 91 Yamazaki et al.

111 3,711,734 1 Jan. 16, 1973 CATHODE-R'AY TUBE HAVING ANTENNA GETTER WITH BIMETALLIC INSERTION DEVICE [75] Inventors: Eiichi Yamazaki, lchihara; Hiromi Kanai, Mobara, both of Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: May 27,1970

211 Appl. No.: 40,774

[30] Foreign Application Priority Data May 30, l969 Japan. .,.44/497l3 (utility model) May 30, I969 Japan. ..,.44/497l4 (utility model) June 2, 1969 Japan ..44/505l2 (utility model) {52] U.S.Cl. ..;..313/l74,3l3/l78,316/19, 29/25.l3 {5i} Int. Cl. ..H01j 19/70, l-lOlj6l/Z6,H0lj 9/18 [58] Field of Search ..3l3/l74, 178,180

{56] References Cited UNITED STATES PATENTS 3,336,502 8/1967 Gilliatt ..3l3/l80 2,843,777 7/l958 Szegho v .3i3/180 X 3,454,8l3 7/1969 Lewinson .,3l3/85 S X Primary Examiner-Robert Sega] Atlorney-Craig, Antonelli & Hill [57] ABSTRACT In cathode-ray tubes provided with an antenna getter on an electron-gun structure, a cathode-ray tube having antenna getter structures so improved in construction that, when the electron-gun structure is advanced for insertion into said cathode-ray tube, there will be eliminated contact between the getter structures and a conductive coating on the inner surface of the tube wall, thereby to protect the conductive coating from coming off or being damaged, whereby deterioration in the inner-electrode insulation due to release of fine particle of the coating into the tube and the Consequent in-tube discharge phenomenon may be prevented,

4 Claims, 10 Drawing Figures PATENTEUJAH 16 1975 3.71 l; 734

sum 1 BF 2 FIG H6. 2

PR/Of? ART PR/Of? ART IN VENTORS sncHl YAMAIAkl AND HIROMI KANAI BY Gag, Hnlinelli, Qluavt 4 Hill ATTORNEYS PATENTEUJAH l 6 I975 SHEET 2 OF 2 F/GT 4a INVENTORS EHCHI YAMALAKI AND HlRoMl KANAI BY (Twig, RnfonellL, slw vl: w HI ATTORNEYS CATHODE-RAY TUBEIIAVING ANTENNA GETTER WITH BIMETALLIC INSERTION DEVICE BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to an improved construction of a cathode-ray tube provided with an antenna getter, and more particularly to a construction of an antenna getter so improved .that it may eliminate contact thereof with a conductive coating on the inner surface of the tube wall when an electron-gun structure is inserted, and a method of manufacturing a cathode-ray tube having such improved construction.

2. Description of the Prior Art In cathode-ray tubes, getter is used in order to maintain a high degree of vacuum in the tube. Particularly in such a cathode-ray tube which is large in the area of the tube inner wall, such as a TV picture tube, it is well known to use getter structures known as an antenna getter or a funnel getter since it is required to form a sufficient amount of getter film over as wide an area as possible.

Generally in a cathode-ray tube, a phsphor screen is provided on the inner face ofya panel portion of the glass bulb, a conductive coating e.g., of graphite for setting up an accelerating electric field is applied and formed on the inner walls of the funnel portion and the neck portion, and an electron-gun structure is disposed coaxially and sealed inthe interior of the neck portion. Elastic strip wires welded to an extreme end of the electron-gun structure extend from the inner wall of the neck portion along the inner wall of the funnel portion, and getter structures are attached to each end of the strip wire at the end remotest from the welded end thereof. Such antenna getter has been suggested in order to extend the getter through the elastic strip wires to substantially the middle of the inner wall of the funnel portion, thereby forming a getter film uniformly and over a wide area on the inner wall of the tube.

However, since the elastic strip wires of this type of antenna getter are formed so as to lie along the inner wall of the tube, they have a tendency to always curve outwardly. Accordingly, in order to insert them through the neck portion into the tube the antenna getter connected to the electron-gun structure, there should be allowed contact between the getter structure and the inner wall of the neck portion due to the nature of the outward curvature of the elastic strip wires. Such advance for insertion of the getter structures under their contact with the inner wall of the neck portion will have the danger of scratching or scraping off the conductive coating which is generally formed on the inner wall over from the central part of the neck portion to the funnel portion for the purpose of setting up an accelerating electric field. Scratching or scraping off the conductive coating will mean that fine particles of the coating may be set free therefrom to fall into the interior of the tube, and the release of the fine particles will become a major cause for deterioration in the inner-electrode insulation or for in-tube discharge in the cathode-ray tube.

SUMMARY OF THE INVENTION It is an object of the invention to provide a cathoderay tube of a construction which has overcome the above-mentioned defects.

Another object of the invention is to provide a cathode-ray tube maintaining the inner-electrode insulation of an electron gun to be normal.

A further object of the invention is to provide a cathode-ray tube stabilized in operation through elimination of one cause for a discharge in the tube.

A still further object of the invention is to provide a method of manufacturing the cathode-ray tubes having the above-mentioned characterizing features.

According to the present invention, there are devised such means that the elastic strip wires of the antenna getter are composed of bimetal, that the elastic strip wires are partially composed of bimetal, that correcting members made of bimetal are provided in a manner to be affixed to the elastic strip wires, or that holding members are provided which engage the elastic strip wires of a conventional antenna getter and which are composed of bimetal, whereby in case the electron-gun structure is advanced and inserted to seal it into the cathode-ray tube, there will be eliminated contact between the getter structures and the conductive coating on the inner wall of the neck portion, whereby the conductive coating is protected from being scraped off or damaged as in the prior art. As a result, there are overcome the previously-mentioned defects occurring in a cathode-ray tube having the prior art construction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view, partly in section, for illustration of a prior art cathode-ray tube.

FIG. 2 is a sectional view, partly broken away, for illustration of the prior art cathode-ray tube.

FIGS. 3a and 3b are illustrative views of an embodiment of an antenna getter for use in the cathode-ray tube according to the invention.

FIGS. 4a and 4b are illustrative views of another embodiment of an antenna getter for use in the cathoderay tube according to the invention.

FIG. 5 is a front view, partly in section, showing a further embodiment of an antenna getter in the cathode-ray tube according to the invention.

FIG. 6 is a front view, partly in section, showing a still further embodiment of an antenna getter in the cathode-ray tube according to the invention.

FIG. 7 is a perspective view of the embodiment shown in FIG. 6, with some parts omitted.

embodiment shown in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiments of the invention, there will now be explained a prior art cathode-ray tube with reference to FIGS. 1 and 2.

In FIG. 1, a glass bulb 1 comprises a panel portion 2, a funnel portion 3 and a neck portion 4. In the neck portion 4, an electron-gun structure 5 is disposed in substantially coaxial relation thereto. Supporting members 11 welded to the electron-gun structure 5 at one extreme end thereof extend from the area of the inner wall of the neck portion 4 along the funnel portion 3, and is provided with a getter structure 7 at the end remotest from the electron-gun structure 5. Since the supporting member 11 supporting the getter structures 7 are made of elastic strip wires 6 so as to extend along the inner wall of the tube, they have a tendency to be always curved outwardly. Accordingly, in order to insert them through the neck portion 4 into the interior of the tube the antenna getter, consisting of the supporting member 1 1 and the getter structure 7, which is connected to the electromgun structure 5, will be allowed, as shown in FIG. 2, to contact the inner wall of the neck portion 4 on account of the nature of the 'outward curvation of the elastic strip wires 6. Such advance for insertion of the getter structures 7 under their contact with the inner wall of the neck portion 4 will scratch or scrape off the conductive coating (not shown) formed on the tube inner wall from the central part of the neck portion 4 to the funnel portion 3, and thus this will set free fine particles from the coating into the interior of the tube to result in bringing about such phenomena as deterioration in the inner-electrode insulation and discharge in the tube.

Referring now to FIGS. 3 to 8, description will be made of the embodiments of the invention.

FIG. 3a is an illustrative view of an embodiment of an antenna getter for use in the cathode-ray tube according to the invention. The embodiment has the same construction as the prior art antenna getter in that elastic strip wires 6 each is welded at one end to an extreme end'of the electron-gun structure 5 and is provided at the other end with the getter structure 7. According to the invention, however, the supporting member 11 consists of an elastic strip wire 6 and a correcting or compensating member 8 made of bimetal, and in this embodiment, the correcting or compensating member 8 made of bimetal is disposed along each elastic strip wire 6. It is well known that a bimetal strip is used to take advantage of the difference in the coefficients of thermal expansion and that it exhibits an expansive or bending phenomenon (hereinbelow termed the bimetal action) due to variations in temperature. It is therefore possible, by e.g., heating the structure as shown in FIG. 3a, to bend the correcting members 8 so as to cause the bending forces to overcome the outwardly curving forces of the elastic strip wires 6 thereby to inwardly curve them. FIG. 3b clearly shows this state. More specifically, the correcting members 8 are brought in proximity in order that the heating thereof may cause them to exert inwardly curving forces upon the elastic strip wires 6, whereby the wires 6 may fall in substantially parallel relation. Accordingly, the getter structure 7 will undergo no such contact with the tube wall as in FIG. 2, if immediately before inserting the electron-gun structure 5 with the antenna getter through the neck portion of the cathode-ray tube, the compensating members 8 made of bimetal and which are affixed onto the elastic strip wires 6 are heated to the state shown in FIG. 3b, and then, the structure 5 having the antenna getter thereon is inserted through the neck portion 4 under these conditions.

FIGS. 4a and 4b are illustrative views of another embodiment. Although the embodiment in FIGS. 3a and 3b has the correcting members 8 affixed onto the elastic strip wires 6, the one shown in FIGS. 4a and 4b uses the compensating members 8 made of bimetal for parts of the elastic strip wires 6 in the supporting members 11 as is apparent from the drawings. FIG. 4b is directed to the state of the compensating members 8 when heated. The object and technical effect of this embodiment are quite the same as those in FIGS. 30 and 3b, and hence detailed explanation thereof is omitted.

FIG. 5 shows a further embodiment, in which the elastic strip wires 6per se forming the supporting.

member 11 are made of bimetal. More specifically, in the process of inserting the electron-gun structure 5 into a predetermined location in the neck portion 4, the elastic strip wires 6 are heated and deflected inwardly as shown, i.e., towards the tube axis (not shown) in such a manner that the getter structures 7 does not come in contact with a conductive coating 10 applied on the inner surface of the neck portion 4. This deflected state is shown in FIG. 5. Again the object and technical result of this embodiment are quite the same as in FIGS. 30 and 3b, and no detailed explanation thereof is made.

Now description will be made of the manufacturing process of the cathode-ray tubes of the embodiments shown in FIGS. 3, 4 and 5, and more particularly, of the step of sealing the electron-gun structure with the antenna getter into the interior of the cathode-ray tube.

First, as shown in FIGS. 3a or 40, the compensating members 8 made of bimetal are affixed to the elastic strip wires 6 or are disposed as parts of the elastic strip wires 6. Alternatively, as shown in FIG. 5, the supporting member 11 made of the elastic strip wires 6 are composed of bimetal. Each elastic strip wires 6-is attached at one extreme end thereof with the getter structure 7 thereby to constitute the antenna getter, and is welded at the other end to an extreme end of the electron-gun structure 5.

Thereafter, the correcting members made of bimetal or the elastic strip wires made of bimetal are heated whereby the elastic strip wires 6 are either brought into substantially parallel relation as shown in FIG. 3b and FIG. 41; or deflected towards the tube axis as shown in FIG. 5 due to the bimetal action, and thus the elastic strip wires 6 as well as the getter structures 7 are located in a cylindrical space having as its bottom the front face 51 of the electron-gun structure 5. With such state maintained, the electron-gun structure 5 attached with the antenna getter is inserted from the open end of the neck portion 4 whilst keeping the coaxial relation to the neck portion. In this case, the getter structure 7 will not come in contact with the inner wall of the neck portion 4 as in the case of FIG. 2. After the correcting members 8 made of bimetal or the elastic strip wires 6 made of bimetal have lowered in temperature, the antenna getter will be displaced in a manner to extend along the inner wall of the neck portion 4 and that of the funnel portion 3, thus providing a construction possessing no difference from that of the prior art cathoderay tube.

FIG. 6 relates to another embodiment of the invention, and shows the correlation between the neck portion 4 and the antenna getter under the state when the electron-gun structure 5 provided with the antenna getter is inserted into the bulb. While the elastic strip wires 6 each welded at one end to the periphery of a front plate 51 of the electron-gun structure 5 will exhibit a tendency to always curve outwardly, they are held through such engagement of holders 9 with the elastic strip wires 6 that the elastic strip wires 6 and the getters 7 each provided at each other end thereof may overcome the force of the spring action and existing within a cylindrical region having as its bottom the front plate 51 of the electron-gun structure 5 (i.e. in FIG. 6, a space determined by the front plate 51 and two-dot chain lines 52). It is FIG. 7 which perspectively shows the state of engagement between the holders 9 and the elastic strip wires 6. In the figure, for brevity of the drawing, only one elastic strip wire 6 and one holder 9 are shown. As apparent from FIG. 7, the holding member 9 extending from the periphery of the front plate 51 extends upwardly and thereafter turns towards the elastic strip wire 6, whereby the extreme end thereof hooks the strip wire 6, and thus the strip wires are forcibly positioned in the cylindrical region. A hole 53 is an electron-beam passing aperture which is formed in the front plate 51. In accordance with the invention, the holder 9 is made of bimetal.

Accordingly, while at normal temperatures the holders 9 made of bimetal engage the elastic strip wires 6 to forcibly hold them as shown in FIGS. 6 and 7, at elevated temperatures the holders 9 have their positions in external form displaced thereby to release the engaging and holding state thereof, with the result that the elastic strip wires 6 will exhibit the inherent nature of the outward curvation. It is FIG. 8 which conceptionally shows such relations in position between the bimetal action and the elastic strip wires. More specifically, at normal temperatures, the holding member 9 made of bimetal lies at a position as shown by the full line, and thereby forcibly holds the elastic wire 6 at a position 61 in a manner that it passes through the cylindrical region. When the holder 9 is raised in temperature under this state, it will be deformed and deflected to a position as shown by dotted line, so the holder 9 and the elastic strip wire 6 are disengaged, with the result that the elastic strip wire 6 will shift to a position 62 owing to the inherent outwardly curving nature thereof.

There will now be described the manufacturing process of the cathode-ray tube of this embodiment, more particularly the step of inserting the antenna getter into the interior of the tube. As has been already explained with reference to FIG. 6, the elastic strip wires 6 are engaged with the holders 9, and then the elastic strip wires 6 as well as the getter structures 7 connected thereto are located in the cylindrical region having the front plate 51 as its bottom and the two twodot chain lines 52 as its edge lines. With such a state maintained, the electron-gun structure Shaving the antenna getter is inserted from the open end of the neck portion 4 while keeping it in a coaxial relation to the neck portion. In this case, the getter structures 7 will not come into such contact with the inner wall of the neck portion 4 as shown in FIG. 2. Accordingly, in the process of this insertion, the getter structures 7 will not advance under the state of contact on the conductive coating which is formed on the inner wall of the neck portion 4 and that of the funnel portion 3, and hence they will not scrape off the coating, with the result that there will be definitely no possibility of giving cause for the in-tube discharge as previously referred to. After completion of the above insertion, a manufacturing step of heat-sealing the open end of the neck portion 4 is performed. The heat at the sealing displaces the ho]- ders 9 made of bimetal from the full-line position to the dot-line position as shown in FIG. 8, thereby to disengage them from the elastic strip wires 6, whereby the elastic strip wires 6 revert in the tube to the position shown in FIG. 1 due to their own outwardly curving nature.

It is of course a matter of fact that the heat-treatment for disengagement between the holders made of bimetal and the elastic strip wires is not restricted to the foregoing sealing heat-treatment, but that it may utilize heat at e.g., a step of exhausting the glass bulb or at the step of flash the getter.

We claim:

1. A cathode-ray tube comprising a glass bulb consisting of a panel portion, a funnel portion and a neck portion of substantially smaller diameter than the average diameter of said funnel portion, a phosphor screen disposed on the inner face of said panel portion, a conductive coating applied and formed on the inner walls of said funnel portion and said neck portion, an electron-gun structure disposed inside said neck portion, at least a pair of antenna getters each including a supporting member secured on one extreme end of said electron-gun structure and a getter structure attached to that end of said supporting member remote from the secured end thereof and being normally positioned closely adjacent said inner wall of said funnel portion, said supporting member having an elastic strip wire and at least a part of said supporting member consisting of a bimetallic member including first and second members of different coefficient of expansion with the member having a higher coefficient of expansion being disposed radially outward from the other member adjacent said glass bulb, said bimetallic member being provided between the center and the secured end of said supporting member whereby upon heating of said bimetallic members said antenna getters will be deflected from their normal position toward the tube axis so as to be spaced by less than the diameter of said neck portion.

2. A cathode-ray tube according to claim 1, wherein said bimetallic members are separate members affixed to said elastic strip wires.

3. A cathode-ray tube according to claim 1, wherein said elastic strip wires are each formed in two parts interconnected by said bimetallic member.

4. A cathode-ray tube comprising a glass bulb consisting of a panel portion, a funnel portion and a neck portion of substantially smaller diameter than the average diameter of said funnel portion, a phosphor screen disposed on the inner face of said panel portion, a conductive coating applied and formed on the inner walls of said funnel portion and said neck portion, an electron-gun structure disposed inside said neck portion, at least a pair of antenna getters each including a supporting member secured on one extreme end of said electron-gun structure and a getter structure attached to that end of said supporting member remote from the secured end thereof and being normally positioned closely adjacent said inner wall of said funnel portion, said supporting member consisting of a bimetallic member including first and second members of different coefficient of expansion with the member having a higher coefficient of expansion being disposed radially outward from the other member adjacent said glass bulb whereby upon heating of said bimetallic members said antenna getters will be deflected from their normal position toward the tube axis so as to be spaced by less than the diameter of said neck portion. 

2. A cathode-ray tube according to claim 1, wherein said bimetallic members are separate members affixed to said elastic strip wires.
 3. A cathode-ray tube according to claim 1, wherein said elastic strip wires are each formed in two parts interconnected by said bimetallic member.
 4. A cathode-ray tube comprising a glass bulb consisting of a panel portion, a funnel portion and a neck portion of substantially smaller diameter than the average diameter of said funnel portion, a phosphor screen disposed on the inner face of said panel portion, a conductive coating applied and formed on the inner walls of said funnel portion and said neck portion, an electron-gun structure disposed inside said neck portion, at least a pair of antenna getters each including a supporting member secured on one extreme end of said electron-gun structure and a getter structure attached to that end of said supporting member remote from the secured end thereof and being normally positioned closely adjacent said inner wall of said funnel portion, said supporting member consisting of a bimetallic member including first and second members of different coefficient of expansion with the member having a higher coefficient of expansion being disposed radially outward from the other member adjacent said glass bulb whereby upon heating of said bimetallic members said antenna getters will be deflected from their normal position toward the tube axis so as to be spaced by less than the diameter of said neck portion. 